CS Book 5_AS- 22 Topaz:Beryl .pdf

Colored Stones 22 KEY CONCEPTS Red and pink topaz varieties, including imperial topaz, are the Price and uniformity are important considerations for buyers most rare and valuable. of treated blue topaz. Color centers and traces of chromium cause th...

Colored Stones 22 KEY CONCEPTS Red and pink topaz varieties, including imperial topaz, are the Price and uniformity are important considerations for buyers most rare and valuable. of treated blue topaz. Color centers and traces of chromium cause the wide variety of The finest aquamarines are a moderately strong, medium- colors in topaz. dark blue to slightly greenish blue. Because many topaz crystals are elongated, they’re often cut Aquamarine generally shows its finest, most saturated color in as long ovals, pears, or emerald cuts. large sizes. Because of its cleavage, topaz requires special care in cutting, Brazil, Pakistan, and China are leading producers of polishing, mounting, and wear. aquamarine. The definitions of imperial topaz can vary widely. Virtually all aquamarine is heat-treated to remove the yellow color component and produce a more marketable blue color. Topaz is commonly colorless, but treatment can produce a blue color. Morganite is almost always heated, or irradiated first and then heated, to produce or improve the pink color. The Ouro Preto area of Brazil is the world’s major commercial source of imperial and red topaz. Traces of manganese cause red beryl’s color. Topaz treatments commonly involve heating or a combination The US state of Utah is the world’s only known source of red of heating and irradiation. beryl. If yellow to reddish brown topaz contains chromium, careful Tone and saturation levels distinguish green beryl from heat treatment can produce a pink color. emerald. Key Terms Imperial topaz—A widely used trade term for gem-quality Precious topaz—A trade term for orange-to-yellow and topaz of medium reddish orange to orange-red color. brown topaz. 44